179 Injectable progesterone priming prior to fixed-time artificial insemination in primiparous and multiparous suckled beef cows
L. B. Ferré A , B. Aguirregabiria B , N. Cerviño C , R. Bello D , M. Jensen A , M. E. Kjelland E F and M. Colazo GA National Institute of Agricultural Technology, Chacra Experimental Integrada Barrow, Tres Arroyos, Buenos Aires, Argentina
B Private Veterinary Practice, Orense, Buenos Aires, Argentina
C CONICET/INTA, Tres Arroyos, Buenos Aires, Argentina
D National University of Tres de Febrero, Caseros, Buenos Aires, Argentina
E Conservation, Genetics & Biotech, LLC, Valley City, North Dakota, USA
F Mayville State University, Mayville, North Dakota, USA
G Livestock Research Section, Alberta Agriculture and Forestry, Edmonton, Alberta, Canada
Reproduction, Fertility and Development 35(2) 217-217 https://doi.org/10.1071/RDv35n2Ab179
Published: 5 December 2022
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
Progesterone (P4) priming may contribute to enhance conception in primiparous and multiparous cows. The aim of this work was to evaluate the effect of a P4 priming 10 days before fixed-time AI (FTAI). Primiparous (Primi), first-calf, Angus cows (24–28 months of age) and multiparous (Multi) Hereford cows (4–6 years of age) weighing 479.33 ± 52.51 kg and 327.38 ± 87.85 kg, with an average body condition score ([BC] scale of 1–5) of 2.83 ± 0.34 and 2.89 ± 1.22, and 59.41 ± 5.47 and 52.47 ± 3.76 days postpartum (PP), respectively, were used. Prior to AI, ovarian status was determined by ultrasound (US) (cycling-CY = corpus luteum-CL, superficial anestrous-SA = follicles ≥ 10 mm and deep anestrous-DA = follicles ≤ 10 mm diameter). On Day 0, animals were randomly divided into two groups considering weight, BC (low = ≤2.5, middle ≥ 2.5, <3.5 and high ≥ 3.5), PP (early ≤ 50, middle ≥ 50 < 55, and late ≥ 55 days) and ovarian status. All cows (Primi P4, n = 29, Multi P4, n = 42; Primi Control, n = 29, Multi Control, n = 44) received 1 g of P4 intravaginal device + 2 mg of oestradiol benzoate. On Day 10, Primi and Multi P4 received an i.m. injection of 60 mg of long-acting P4. On Day 7, the device was removed + i.m. 150 ug of D-cloprostenol + 1 mg of oestradiol cypionate and tails were painted. All cows were inseminated by a single proven fertility bull and inseminator on Day 9 (50–52 h post-device removal). The pregnancy diagnosis was performed 35 days after FTAI by US. Data were compared by Pearson’s chi-squared test (α = 0.05). Overall pregnancy rates did not differ between Primi P4 (72.4% [21/29]) and Primi Control (69.0% [20/29]) as well as Multi P4 (59.5% [25/42]) and Multi Control (59.1% [26/44]). BC, PP, ovarian status, and oestrus expression did not affect the pregnancy rate in primiparous and multiparous suckled cows. Injectable Primi P4 tended numerically to be more effective in cows with low BC, early PP, and SA; while injectable Multi P4 in cows with low BC, DA and in cows in oestrous at the time of FTAI. P4 priming did not significantly improve the analysed variables. Notably, the trend was for low BC in the P4 to perform better in both primiparous and multiparous suckled cows than the control. P4 concentration and timing may need to be adjusted and a larger sample size is needed for future studies.
